Composition with latent reactive catalyst

Abstract

Thermosetting compositions comprising a film forming component bearing or capable of generating hydroxyl functionality, amine-aldehyde crosslinking agent, and a latent reactive catalyst comprising the reaction product of (i) a copolymer bearing pendent epoxy functionality, and (ii) a sulfonic acid having the formula ##STR1## wherein R is selected from linear or branched alkyl groups and aryl groups. Preferred compositions within the scope of the invention include high solids, thermosetting coating compositions suitable for automotive applications.

What is claimed is: 
     
       1. A liquid, thermosetting high solids coating composition which is adapted for low temperature bake applications, which contains greater than about 55% by weight of nonvolatile solids, and which, exclusive of pigments, solvents and other nonreactive components, consists essentially of: (A) a bifunctional copolymer bearing hydroxyl functionality and pendent epoxy functionality, having a number average moleculer weight (M n ) of between about 1,500 and about 10,000 and a glass transition temperature (T g ) of between about -25° C. and about 70° C., said copolymer consisting essentially of (i) between about 5 and about 25 weight percent of monoethylenically unsaturated monomers bearing glycidyl functionality and between about 5 and about 25 weight percent of monoethylenically unsaturated monomers bearing hydroxyl functionality, with the total of said glycidyl and hydroxy functional monomers being not greater than about 30 weight percent of other monoethylenically unsaturated monomers in said bifunctional copolymer and (ii) between about 90 and about 70 weight percent of other monoethylencially unsaturated monomers;   (B) a latent reactive catalyst comprising the reaction product of (i) a monofunctional copolymer bearing pendent epoxy functionality, having a number average molecular weight (M n ) of between about 1,500 and about 10,000 and a glass transition temperature (T g ) of between about -25° C. and about 70° C., said copolymer being prepared from between about 5 and about 30 weight percent of monoethylenically unsaturated monomers bearing glycidyl functionality and between about 70 and about 95 weight percent of other monoethylenically unsaturated monomers; and (ii) a sulfonic acid having the formula ##STR5##  wherein R is selected from linear or branched alkyl groups and aryl groups, said copolymer bearing pendent epoxy functionality and said sulfonic acid being reacted in such amounts that there are between 0.3 and about 1 acid groups per epoxy in the reaction mixture.   (C) an amine-aldehyde crosslinking agent; and   (D) up to about 45 weight percent of a hydroxy functional additive having a member average molecular weight (M n ) of between about 150 and about 6,000, said latent reactive catalyst being included in said composition in an amount ranging from about 0.5 to about 5 weight percent, said amine-aldehyde crosslinking agent being included in said composition in an amount ranging from about 15 to about 45 weight percent, said weight percents being based on the total weight of (A), (B), (C) and (D).     
     
     
       2. A composition in accordance with claim 1 or wherein said monoethylenically unsaturated monomers bearing glycidyl functionality and used in preparing said copolymer (A) are selected from glycidyl esters and glycidyl ethers. 
     
     
       3. A composition in accordance with claim 2 wherein said monoethylenically unsaturated monomers bearing glycidyl functionality are selected from glycidyl esters of monoethylenically unsaturated carboxylic acids. 
     
     
       4. A composition in accordance with claim 1 wherein said monoethylenically unsaturated monomers bearing hydroxyl functionality in said bifunctional copolymer are selected from the group consisting of hydroxyalkyl acrylates formed by the reaction of C 2  -C 5  dihydric alcohols and acrylic or methacrylic acids. 
     
     
       5. A composition in accordance with claim 1 or wherein said other monoethylenically unsaturated monomers used in preparing said copolymer (A) are selected from the group consisting of acrylates and other monoethylenically unsaturated vinyl monomers. 
     
     
       6. A composition in accordance with claim 5 wherein said acrylate monomers comprise at least about 50 weight percent of the total monomers in said copolymer and are selected from the group consisting of esters of C 1  -C 12  monohydric alcohols and acrylic or methacrylic acids. 
     
     
       7. A composition in accordance with claim 1 wherein said monoethylenically unsaturated monomers bearing glycidyl functionality and used in preparing said copolymer employed in the preparation of said latent reactive catalyst are selected from glycidyl esters and glycidyl ethers. 
     
     
       8. A composition in accordance with claim 7 wherein said monoethylenically unsaturated monomers bearing glycidyl functionality are selected from glycidyl esters of monoethylenically unsaturated carboxylic acids. 
     
     
       9. A composition in accordance with claim 8 wherein said glycidyl esters are esters of acrylic or methacrylic acids. 
     
     
       10. A composition in accordance with claim 7 wherein said copolymer bearing pendent epoxy functionalityand said sulfonic acid employed in the preparation of said latent reactive catalyst are reacted in such amounts that there are between about 0.5 and about 0.9 acid groups per epoxy in the reaction mixture. 
     
     
       11. A composition in accordance with claim 1 or wherein said other monoethylenically unsaturated monomers used in preparing said copolymer employed in the preparation of said latent reactive catalyst are selected from the group consisting of acrylate monomers and other monoethylenically unsaturated vinyl monomers. 
     
     
       12. A composition in accordance with claim 11 wherein said acrylate monomers used in preparing said copolymer employed in preparation of said latent reactive catalyst comprise at least about 50 weight percent of the total monomers in said copolymer. 
     
     
       13. A composition in accordance with claim 1 or wherein said amide-aldehyde crosslinking agent is selected from the group consisting of condensation products of formaldehyde with melamine, substituted melamine, urea, benzoguanamine, and substituted benzoguanamine, and mixtures of said condensation products, and is included in an amount of between about 15 and about 45 weight percent based on the total weight of (A), (B), (C) and (D). 
     
     
       14. A composition in accordance with claim 1 or wherein said hydroxyl functional additive is selected from the group consisting of (i) hydroxyl functional polyesters, (ii) hydroxyl functional polyethers, (iii) hydroxyl functional oligoesters, (iv) monomeric polyols, (v) hydroxyl functional copolymers formed from monoethylenically unsaturated monomers, one or more of which bears hydroxy functionality and which is included in said copolymer in amounts ranging from about 10 to about 30 weight percent of said copolymer, and (vi) mixtures of (i)-(v).